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At least 163 records · Page 9Linked to original sources
PubMed1979

Thorium dioxide granuloma of the neck with resultant fatal hemorrhage.

A 46-year-old man had a granuloma in the neck that was caused by extravasation of thorium dioxide (Thorotrast) by an angiographic procedure performed about 30 years previously. His chief complaints were dysphagia and dyspnea with mild hoarseness. Parital resection of the tumor was performed, but his symptoms were not ameliorated. The immediate postoperative course was unfavorable. The patient died four months after the operation from massive hemorrhages from the right common carotid artery.

Carotid Arteries↗
PubMed1981

Positive colloidal thorium dioxide as an electron microscopical contrasting agent for glycosaminoglycans, compared with ruthenium red and positive colloidal iron.

In electron microscopy Thorotrast has been used as a specific contrasting agent for acid glycosaminoglycans. Because of its high atomic number, thorium (Z=90) gives good contrast in the electron microscope, but at present it is less frequently used for this purpose. We prepared a positive colloidal solution of ThO2 without stabilizers to compare its properties with those of ruthenium red and positive colloidal iron for contrasting fetal mouse epiphyseal cartilage. The results indicate that colloidal ThO2, which is easy to prepare in any laboratory, gives better results than ruthenium red and colloidal iron do in this kind of cartilage. Furthermore, as judged from data in the literature and obtained in our laboratory, it penetrates this tissue better than Thorotrast does, probably because of the absence of stabilizers.

Animals↗
PubMed1975

Pinocytotic uptake and intracellular distribution of colloidal thorium dioxide by cultured sensory neurites.

Sensory ganglia from 9-day chick embryos were grown on collagen coated coverslips for36 h in the presence of nerve growth factor, producing a profuse neuritic outgrowth. The cultures were then incubated for varying periods in a colloidal suspension of thorium dioxide, and the pinocytotic uptake of this marker was followed by electron microscopy. Following brief exposures (3 min), most of the labelled organelles consisted of smooth surfaced vesicles and vacuoles; with longer exposures, the bulk of the marker accumulated first in cup-shaped pre-multivesticular bodies and ultimately in multivesicular bodies. The marker was also taken up into coated vesicles, dense-cored and electron lucent tubules,dense-cored vesicles and dense bodies of the multi-layered myelin body configuration. In addition, evidence suggestive of exocytosis was also obtained; views of apparent fusion of labelled multivesicular bodies with the plasmalemma involving extrusion of vesiclesand marker particles into the extracellular space were regularly encountered following long exposures.

Animals↗
PubMed1999

Acquisition of improved reference values for cesium, iodine, strontium, thorium, and uranium in selected NIST reference materials.

As part of a study on the ingestion and organ content of some trace elements of importance in radiological protection, additional work has been undertaken to acquire improved reference values for cesium, iodine, strontium, thorium, and uranium in four selected reference materials provided by the US National Institute of Standards and Technology. The materials are SRM-1548 Total Diet, SRM-1548a Typical Diet, SRM-1486 Bone Meal, and RM-8414 Bovine Muscle. A coordinated study was undertaken with the help of seven selected laboratories in five countries. Instrumental and radiochemical neutron activation analysis and inductively coupled plasma-mass spectrometry were the analytical main techniques used.

Animals↗
PubMed2005

Flow-injection technique for determination of uranium and thorium isotopes in urine by inductively coupled plasma mass spectrometry.

A sensitive and efficient flow-injection (FI) preconcentration and matrix-separation technique coupled to sector field ICP-mass spectrometry (SF-ICP-MS) has been developed and validated for simultaneous determination of ultra-low levels of uranium (U) and thorium (Th) in human urine. The method is based on selective retention of U and Th from a urine matrix, after microwave digestion, on an extraction chromatographic TRU resin, as an alternative to U/TEVA resin, and their subsequent elution with ammonium oxalate. Using a 10 mL sample, the limits of detection achieved for 238U and 232Th were 0.02 and 0.03 ng L(-1), respectively. The accuracy of the method was checked by spike-recovery measurements. Levels of U and Th in human urine were found to be in the ranges 1.86-5.50 and 0.176-2.35 ng L(-1), respectively, well in agreement with levels considered normal for non-occupationally exposed persons. The precision obtained for five replicate measurements of a urine sample was 2 and 3% for U and Th, respectively. The method also enables on-line measurements of the 235U/238U isotope ratios in urine. Precision of 0.82-1.04% (RSD) was obtained for 235U/238U at low ng L(-1) levels, using the FI transient signal approach.

Flow Injection Analysis↗
PubMed1978

Vascular complications of thorium dioxide.

Vascular complications occurring late after exposure to thorium dioxide (thorotrast) are described in two patients. One patient had both cerebral andmyocardial infarcts and died at age 25 years. Necropsy disclosed both adventitial and intimal fibrosis of the left carotid artery and greater than 75 per cent cross-sectional area luminal narrowing of both the left main and left anterior descending coronary arteries. The other patient, a 33 year old man, had no cerebral symptoms in life but total obstruction of the right carotid artery secondary to a thorotrastoma was found at necropsy. Vascular complications due to thorotrast appear to represent consequences of chronic alpha irradiation.

Adult↗
PubMed1978

A review of parameter values used to assess the transport of plutonium, uranium, and thorium in terrestrial food chains.

A general methodology of predicting the food chain transport of atmospherically deposited radionuclides is reviewed with an emphasis on variation in parameter values important for realistic behavioral characterization of environmental releases of plutonium, uranium, and thorium. Parameters important to generic simulations of food chain transport, given a known constant deposition onto vegetation, include: fractional interception of particulates by vegetation, vegetation density, effective half-life of contamination on vegetation, soil-to-plant transfer factors, consumption rates by cattle and man, and transfer of nuclides from forage to meat and from forage to milk. Variation in these parameters, which has been encountered in field studies, is summarized. A partial reduction in the variation of predicted concentrations of actinides in foods can be accomplished by more accurately determining critical parameter values like fractional interception of deposition by vegetation, vegetation biomass, and the effective half-life of contamination on vegetation. Field research describing the site dependency and time dependency of probability density functions for model parameter values is needed to make probabilistic predictions concerning Pu, U, and Th transport in food chains and to reduce the uncertainty associated with model predictions and generic assessments of environmental impact.

Biological Transport↗
PubMed1989

Assimilation of thorium isotopes into terrestrial vegetation.

Vegetation and root zone soil from 17 locations within and near the boundaries of a former thorium processing plant were collected and analyzed for 232Th, 228Th and 230Th in order to evaluate the degree of movement of these radionuclides from soil to root tissue, as well as the extent of their translocation into above-ground plant compartments. Concentration ratio (CR) values ranged as follows: 232Th: 0.0003-0.3218 (shoots), 0.0065-0.9057 (roots); 228Th: 0.0038-0.3300 (shoots), 0.0183-0.7335 (roots); 230Th: 0.0007-0.4560 (shoots), 0.0076-1.252 (roots). Root/shoot ratios were 1.03-85.6 (232Th), 1.54-45.8 (228Th) and 1.36-54.5 (230Th). In nearly all instances, the CR values for 228Th exceeded those for 232Th, with the average 228Th/232Th CR ratios being 3.36 and 1.68 for shoots and roots, respectively. No discernable difference was observed between 230Th and 232Th concentration patterns. The increased 228Th/232Th CR ratio observed is presumably due to the intake of 228Ra into the plant structure, leading to subsequent production of 228Th, through decay, within the plant. It is estimated that approximately 80% of the resident 228Th in above-ground vegetation originates through this mechanism.

Illinois↗
PubMed2006

An improved radiochemical separation of uranium and thorium in environmental samples involving peroxide fusion.

A radiochemical procedure for the accurate determination of uranium and thorium using peroxide fusion followed by ion exchange and extraction chromatography is described. The method of extraction of the element from solid samples is the most important factor in the investigation. It is demonstrated, by measuring a number of reference materials, that fusion with Na(2)O(2) ensures a complete destruction of the mineral lattice and greatly improves the determination of the true activity of actinides.

Chromatography, Ion Exchange↗
PubMed2004

Uranium-thorium disequilibrium in north-east Atlantic waters.

In this paper we report and compare the concentrations of 234Th and 238U measured in surface and subsurface waters collected in the course of a sampling campaign in the north east Atlantic in June-July 1998. Dissolved 234Th concentrations in surface waters ranged from 5 to 20 Bq m(-3), showing a large deficiency relative to 238U concentrations (typically 42 Bq m-3). This disequilibrium is indicative of active 234Th scavenging from surface waters. Observed 234Th/238U activity ratios, together with corresponding 234Th particulate concentrations, were used to calculate mean residence times for 234Th with respect to scavenging onto particles (tau(diss)) and subsequent removal from surface waters (tau(part)). Residence times in the range 5-30 days were determined for tau(diss) and 4-18 days for tau(part) (n=14). In addition, ultrafiltration experiments at six stations in the course of the same expedition revealed that in north-east Atlantic surface waters a significant fraction (46+/-17%; n=6) of the thorium in the (operationally-defined) dissolved phase (<0.45 microm) is in colloidal form. These observations are consistent with the 'colloidal pumping' model in which it is assumed that 234Th is rapidly absorbed by colloidal particles, which then aggregate, albeit at a slower rate, into larger filterable particles. In essence, colloids act as intermediaries in the transition from the fully dissolved to the filter-retained (>0.45 microm) phase. Thus, the time (tau(c)) for fully dissolved 234Th to appear in the filter-retained fraction is dependent on the rate of colloidal aggregation. Here, we determined tau(c) values in the range 3-17 days.

Atlantic Ocean↗
PubMed2006

Sequential separation of lanthanides, thorium and uranium using novel solid phase extraction method from high acidic nuclear wastes.

A novel grafted polymer for selective extraction and sequential separation of lanthanides, thorium and uranium from high acidic wastes has been developed by grafting Merrifield chloromethylated (MCM) resin with octyl(phenyl)-N,N-diisobutylcarbamoyl-methylphosphine oxide (CMPO) (MCM-CMPO). The grafting process is well characterized using FT-IR spectroscopy, (31)P and (13)C CPMAS (cross-polarized magic angle spin) NMR spectroscopy and CHNPS elemental analysis. The influence of various physico-chemical parameters during metal ion extraction by the resin phase are studied and optimized by both static and dynamic methods. The resin shows very high sorption capacity values of 0.960mmolg(-1) for U(VI), 0.984mmolg(-1) for Th(IV), 0.488mmolg(-1) for La(III) and 0.502mmolg(-1) for Nd(III) under optimum HNO(3) medium, respectively. The grafted polymer shows faster rate exchange kinetics (<5min is sufficient for 50% extraction) and greater preconcentration ability, with reusability exceeding 20 cycles. During desorption process, sequential separation of the analytes is possible with varying eluting agents. The developed grafted resin has been successfully applied in extracting Th(IV) from high matrix monazite sand, U(VI) and Th(IV) from simulated nuclear spent fuel mixtures. All the analytical data is based on triplicate analysis and measurements are within 3.5% rsd reflecting the reproducibility and reliability of the developed method.

Lanthanoid Series Elements↗
PubMed2005

Structural and thermal characterization of cerium, thorium and uranyl complexes of sulfasalazine.

Cerium(IV), Thorium(IV) and Uranyl(II) complexes with the ammonium salt of sulfasalazine drug (H2SSZ, HL-) have been studied. The structures of the complexes were elucidated using elemental analysis, IR and mass spectroscopy and thermal analysis. The complexes were isolated in 1:1 and 1:2 (M:L) ratios. The solid monocomplexes (1:1) (M:H(2)SSZ) were isolated in the general formulae [UO2(L)(H2O)2].2H2O and [M(L)(X)z(H2O)n].yH2O (M=Ce(IV) and Th(IV) (X=NO3, z=2, n=2, y=0-3)). The biscomplexes (1:2) (M:H2SSZ) solid chelates found to have the general formulae [UO2(HL)2].2H2O and [M(L)2(H2O)2] (M=Ce(IV) and Th(IV)). The thermal decomposition of the complexes should be discussed in relation to structure, and the thermodynamic parameters of the decomposition stages were evaluated applying Coats-Redfern and Horwitz-Mitzger methods.

Cerium↗
PubMed2005

Uranium and thorium in weathering and pedogenetic profiles developed on granitic rocks from NW Spain.

Uranium and thorium were analyzed in seven weathering and pedogenetic soil profiles developed on granitic rocks from NW Spain. Concentrations were measured by X-ray fluorescence spectrometry (XRF) and the U- and Th-bearing minerals were studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). Both elements were determined in rock, bulk soil and in different grain-size fractions (sand: 2000-50 microm, silt: 50-2 microm, and clay: <2 microm). U concentrations in the rock varied between 5.3 and 27.7 mg kg(-1) and Th concentrations from 5.5 to 50.7 mg kg(-1). The most alkalic rocks can be considered as U-rich granites. Bulk soil U and Th concentrations are similar to those of the rocks (4.8-29.2 and 7.4-56.7 mg kg(-1), respectively), but in the grain-size fractions both elements show the lowest concentrations in the sand and the highest in the clay. In the latter, concentrations are always higher than those of the rocks, particularly in the C horizons with enrichments up to 4 times for U and 5 times for Th. The concentration profiles and the ratios to the parent rock suggest that U and Th are leached from the surface soil and accumulate in the deeper horizons. Mass balance calculations, using Ti as a reference immobile element, also support U and Th leaching in the solum and supergene enrichment in bottom horizons. Leaching seems to be more intense on horizons with gravel content higher than 20%. The leaching of U and Th in the topmost horizons and the accumulation in the bottom soil horizons can be considered as a natural attenuation of the impact of these radiogenic elements in the environment. But their enrichment in the potentially airborne fraction poses some risk of redistribution in the ecosystems.

Environmental Monitoring↗
PubMed2001

Scavenging of thorium isotopes in the Arctic regions: implications for the fate of particle-reactive pollutants.

The sources of inorganic pollutants to the Arctic areas are reviewed using previously published results. The removal of particle-reactive pollutants is discussed using thorium scavenging as an analog. The scavenging of 234Th from the upper water column (approximately 100 m) and sediment inventory of 230Th from the deep Arctic waters is compared to different ocean basins in the subarctic areas. Such a comparison shows that 234Th is in equilibrium with its parent, 238U, in certain regions of the Canada Basin of the Arctic Ocean, while it is deficient in other regions of the arctic as well as in sub-polar ocean basins. This implies that the particle-reactive pollutants in the deep Arctic of the Canada Basin are less likely to be removed from the deep waters and will eventually be transported out of this area. We have utilized the 230Th inventory in sediments from the Arctic area to determine the removal rates of particle-reactive nuclides. The 230Th inventory in the deep Arctic Ocean of the Canada Basin is much lower than the Norwegian Sea and the Fram Strait of the Arctic as well as all other sub-polar world oceans. These observations suggest that any pollutants into the deep Arctic areas of the Canada Basin are less likely to be removed locally and may be transported out of this area. In those areas, the colloidal material could potentially play a major role in the removal of particle-reactive contaminants.

Arctic Regions↗
PubMed2002

Intercomparison of INAA and ICP-MS results for thorium determination in Pakistani diet.

A pilot study on ingestion and organ content of trace elements of importance in radiological protection was to be carried out in Pakistan. Baseline analytical data on daily dietary intake of thorium was to be measured using Instrumental Neutron Activation Analysis (INAA) technique. To determine the accuracy and reliability of our technique, some samples were measured in Pakistan using INAA and in Japan using Inductively Coupled Plasma-Mass Spectrometry. For intercomparison of results overall mean Z-scores were calculated. The results showed validity of our technique. Mean value of 232Th concentration in Pakistani diet samples using INAA technique is 0.0062 +/- 0.0028 microg/g and with ICP-MS technique is 0.0069 +/- 0.0032 microg/g.

Diet↗
PubMed2003

Uranium and thorium series radionuclides in rainwater over several tropical storms.

The activity concentrations of uranium and thorium series radionuclides were measured in rainwater samples from 16 storms in northern Australia. For six of these storms, sequential intra-storm samples were collected. The results indicate that a substantial fraction of the measured activity concentrations of 238U, 234U, 230Th, 226Ra and, to a lesser extent, 210Po were due to below-cloud washout of dust transported from the nearby Ranger uranium mine. For the six intra-storm studies, the concentrations of these dust-related radionuclides decreased to one half or less of their initial value after the first one to two millimetres of rainfall, although in some cases they later increased when the rainfall intensity reduced. Most of the 210Pb activity appears to have been sourced from in-cloud rainout, although below-cloud washout was probably responsible for significant reductions in concentrations observed over the course of three of the six storms. 210Pb residence times based on the 210Pb-210Po couple varied significantly from storm to storm, but relatively little over the course of each of the six storms studied in detail. This implies that, apart from the initial reduction in below-cloud washout, there was no substantial change in the source air mass for the 210Pb during these storms.

Australia↗
PubMed2003

Thorium removal by different adsorbents.

The removal of radiotoxic Th(4+) from aqueous solutions has been explored using two different groups of adsorptive materials (e.g. two activated carbons and four zeolites-two natural and two synthetic). The activated carbons were prepared from solvent extracted olive pulp (SEOP) and olive stone (OS) by a two-step physical activation method with steam. They were characterized by N(2) at 77K adsorption, Hg porosimetry and by determination of their iodine number. All carbons prepared are of the H-type (e.g. contain mainly basic surface oxides) confirmed by the results of the Boehm's method. The natural zeolites, clinoptilolite (NaCLI) and mordenite (NaMOR), were pretreated with Na(+) before the adsorption experiments, while the synthetic ones, NaX and NaA, were provided in their commercial sodium form. The natural zeolites, NaCLI and NaMOR, utilized 11.5 and 38.6% of the theoretical ion-exchange capacity, based on Al content, respectively, while NaX and NaA utilized 41.5 and 45.9%, respectively. The activated carbons showed better removal capability than NaCLI. NaMOR, showed comparable results to the carbon originated from OS, but lower removal capability than the carbon originated from SEOP. The synthetic zeolites showed the highest removal ability for thorium ions due to their increased ion-exchange capacity because of their cleaner and larger framework channels and their higher number of ion-exchange sites. The carbons adsorption capacity mainly depends on the content and nature of functional surface groups. The adsorption data were fitted to Langmuir and Freundlich models. The former achieved best fits and was further applied to obtain the respective Langmuir constant and maximum adsorption capacity for each system.

Adsorption↗
PubMed2001

Concerning the low uranium and thorium yields in the electrodeposition process of soil and sediment analyses.

The very low yields obtained in a common method of alpha-particle spectrometry for the determination of uranium and thorium in soil and sediment samples of environmental origin were investigated. Several experiments were performed to determine the cause. The results suggest that aluminium may cause major chemical interference in the electrodeposition process, and can be considered to be primarily responsible for the low recoveries found. A procedure is proposed to resolve this problem.

Alpha Particles↗